1. Field of the Invention
This invention relates to a ceramic substrate of a semiconductor package used to seal semiconductor elements airtightly, having a feature suited to prevent the generation of chipping defects and cracks in the ceramic substrate due to the impact of ceramic substrates with each other, especially during assembly and transportation of the semiconductor packages.
2. Description of the Prior Art
Conventionally, as a substrate for semiconductor package as shown in FIG. 1(a), a ceramic substrate 1 formed as a flat plate with a nearly rectangular parallelpiped shape having a cavity 4 engraved in the back center has widely been used due to its excellent performance in electric insulation, chemical stability, wear resistance, hardness, coefficient of thermal expansion, etc. Although ceramic materials have many quite superior characteristics as used as packages of semiconductors, such also are notable for their deficiency in causing a chipping defect A or crack B in the edge 2 or corner portion 3 of ceramic substrate 1 when the same is connected to semiconductor package 5 as shown in FIG. 1(a) and 1(b) as a result of mutual impact of the ceramic substrates 1 in the transportation and assembly of the semiconductor packages. Such chipping defect A and crack B are apt to occur especially to a portion of the sharp edge, i.e. edge portion 2 or corner portion 3 of ceramic substrate 1, causing various problems such as a reduction in the reliability of semiconductor package 5.